USE OF A MICRO ELECTRODE TO STUDY THE ELECTROCHEMICAL BEHAVIOUR OF THE MICRO PHASES IN 20 STEEL AND 16Mn STEEL
用微电极研究20钢和16Mn钢微区相电化学行为

The polarization curves of the phases in 20 steel and 16Mn in 1 mol/L NaNO 3 were measured by using a Ag/AgCl micro electrode. The potentials at zero current of ferrite, pearlite and mixed phase corresponded to the mixed potential theory. The sequence of the potential from positive to nagative was ferrite, mixed phase and pearlite. The corrosion current density of the phases increased in the above order. In situ observation of the corrosion process of the mixed phase showed that pearlite corroded preferencially. Pearlite and ferrite in the mixed phese formed a micro electrochemical cell because of the potential difference between the two phases, which accelerated the corrosion of pearlite and inhibited the corrosion of ferrite phase.